Millions of pounds of charity donations and taxpayers' money have been wasted on worthless cancer studies, the BBC has learned.

File On 4 has discovered thousands of studies have been invalidated.

It found some scientists have failed to carry out simple and inexpensive checks to ensure they are working with the right forms of human tumour cells.

Cancer Research UK said it used robust procedures to check the cell-lines used in research.

One of the latest examples of scientific research to be affected by this problem is a study of oesophageal cancer.

Researcher Dr Chris Tselepis worked with an international team which has found that TE7, an experimental culture of cancer cells used in labs for the past 20 years, was the wrong cancer.

Whole programmes of research had to be redone using verified human brain tumour cells
Prof Geoff Pilkington, University of Portsmouth

"Fortunately, for us our research was based on a number of cell types, so the impact of a mistaken identity for this line has actually been fairly minimal to us," said Dr Tselepis who is studying the cancer at the Cancer Research UK laboratories in Birmingham University.

"But I'm sure there's many other laboratories UK and worldwide-based that essentially base lots of their conclusions on one cell line and in that case, this mistaken identity has a massive impact on conclusions that people draw from such studies," he added.

Few scientists publicly admit such problems but Prof Geoff Pilkington, of the University of Portsmouth, told the BBC that he had to discard research into brain tumours after it emerged his team were studying human cells contaminated by the cells of rats and mice.

"Whole programmes of research had to be redone using verified human brain tumour cells," he said.

The problem is compounded by the fact that studies based on erroneous research data will be printed in reputable scientific journals and become part of the accepted literature, thus misleading future researchers.

Earlier this year 19 eminent cancer specialists from the UK and USA wrote to the US health secretary urging tough action to end this waste of time, effort and money.

The US authorities replied that there appeared to be "abundant evidence" that many studies and publications had been compromised.

But the letter's originator, Prof Roland Nardone of the Catholic University of America, told the BBC that some scientists seemed unwilling to act.